Production of gases containing sulfur dioxide



A.JOHANNSEN ET AL 2,825,628

PRODUCTION OF GASES CONTAINING SULFUR DIOXIDE Filed Dec. 14, 1953 WASTE HEAT BOILER INVENTORS'. ADOLF JOHANNSEN WILL! DANZ WILL! KLINGLER BY @Me Mr 277 ATT'YS March 4, 1958 FROM BLOWER United States Patentfi PRODUCTION OF GASES CONTAINING SULFUR DIOXIDE Adolf Johannsen, Ludwigshafen (Rhine), Willi Dana, Ludwigshafen (Rhine) Oggersheim, and Willi Klingler, Ludwigshafen (Rhine), Germany, assigners to Badlsche Anilin- & Soda-Fabrik Aktiengesellschafi, Ludwigshafen (Rhine), Germany Application December 14, 1953, Serial No. 398,188

.Claims priority, application Germany December 12, B52

8 Claims. (Cl. 23-177) This invention relates to a new and improved process for the production of gases containing sulfur dioxide. In the roasting of granular sulfidic ores, having a grain size of, for example, to 6 mm., by the turbulent layer or fluidized bed process, a part of the roasted material, in particular the fines, is carried away from the furnace with-the roaster gas current, and deposited in subsequent dust separators, while the coarser-grain fraction of the roasted material is removed directly from the turbulent layer. By providing for an overflow at different distances from the grate, it is possible to vary the height of the turbulent layer itself. A convenient method of processing is' by removing roasted material continuously from the turbulent layer as the sulfidic ore is continuously fed thereinto, so that the turbulent layer is kept at a constant level and as a result the discharge of heat with the aid of cooling devices built into the turbulent layer remains constant.

On the contrary, in the roasting of very finely grained sulfidic ores, in particular of flotation concentrates having grain sizes of less than 0.2 mm., the whole of the roasted pulverulent material is carried out of the furnace by the roaster gases when maximum throughputs and the consequent high gas speeds in the roasting chamber are worked with. By the vivid turbulence in the roasting layer, which is composed of loose-textured agglomerates in admixture with very fine material, the agglomerates are broken up and also entrained by the gas, in the form of dust, while the level of the turbulent bed is maintained by a fresh feed of agglomerates. In general the depth of the layer must be kept lower in the roasting of flotation concentrates than in the roasting of granular material and cannot be raised at will. As a result, the quantity of heat that can be withdrawn from the turbulent layer with the aid of inbuilt cooling elements and utilized will be smaller than .in the case of greater depths.

Our invention aflords a new and eficient technique to overcome the shortcomings attendant upon the roasting of fine-grained sulfidic ores, more specifically flotation concentrates, in a layer of the roasted material kept in random turbulent motion and uniformly loosened up by the oxygen-containing gases needed for the roasting which are introduced from below and by the roaster gas. This technique comprises introducing into the turbulent layer, additionally to the main supply of the oxygen-containing gases introduced uniformly from below, subordinate proportions of oxygen-containing gases at one or more separate points other than those at which the main supply is made. By this additional feed of air or air enriched with oxygen, which can be introduced into the turbulent layer, either by blowing or sucking, at some points thereof, whether from above or from below or from the side, a blast effect will result, giving rise to local overheating with a consequent more or less marked agglomeration of the particles to be roasted. By the turbulent motion, these agglomerated particles are very fast distributed over the entire turbulent layer, so that the formation of relatively large-sized conglomerates which would interfere with the turbulent motion, is prevented. in a preferred embodiment of our invention the additional feed of oxygen-containing gas into the turbulent layer is done near the point where the feed of the sulfidic ore into the layer takes place, because at this point the concentration of roastable sulfur and consequently the agglomeration eifect are at their highest.

An alternative embodiment of our invention provides for very finely-divided roasting material, in particular sulfidic flotation concentrates, to be introduced into the turbulent layer together with the additional feed of oxygen-containing gas. This common feed can be carried out with mixing burners. By this means local increases in temperature can be effected which are the prerequisite for the formation of agglomeration centres.

The favorable influence of a partial agglomeration of the roasting material on the properties of the turbulent layer can be markedly enhanced by introducing into the turbulent layer, together with the oxygen-containing gases which are additionally fed thereinto, roasted ore withdrawn from the turbulent layer and/or the coarsergrained portion of the flue cinders, i. e. the roasted ore which is entrained away from the turbulent layer with the roaster gases and/ or roasted ore of similar grain size from other roasting systems.

In order to avoid any appreciable heat losses during the introduction of said cinders into the turbulent layer, the cinders should be introduced as far as possible at the temperatures which they have when leaving the turbulent layer and/or the dust separators and/ or the other roast- 'ing systems from which they are Withdrawn.

The cinders can also be fed into the turbulent layer after having been thoroughly mixed with very fine-grained roasting material. For the feed of the cinders in the form of a mixture with very fine-grained roasting material, it is desirable that the mixing should be done with the cinders being in a hot state, as this will effect a predrying of the roasting material, which is usually moist, and result in a shaping of the fine-grained material to coarser grains by the formation of crusts on the surface of the particles of the roasted ore before this is fed into the turbulent layer.

The mixture of the cinders and the very fine-grained roasting material can also be supplied to the turbulent layer suspended in the oxygen-containing gases additionally introduced.

In the practice of our invention the quantity of cinders which is fed, returned or recycled into the turbulent layer with the oxygen-containing gases additionally supplied, should amount to about 20 to 40% of the cinders being formed in the turbulent layer by the roasting of the ore.

For the separation of the coarser-grained constituents of the flue cinders entrained with the roaster gases simple impact separators, for example, can be used. The flue passes of the waste heat boilers arranged behind the furnace can, when suitably constructed, serve as separators of this type.

By the coarsening of the grains in the turbulent layer as a result of our invention, the height of the turbulent layer fed with most finely grained sulfidic ores can be increased and kept constant. This makes the roasting operation safer or makes it possible at all, as the circumstances may be. Moreover, when the turbulent layer is of suflicient height and maintained constant, more heat can be withdrawn therefrom by cooling elements built into the layer.. As the height of the turbulent layer can be varied in accordance with the service conditions, a greater elasticity of the furnace production is obtained. With higher throughputs through the furnace, the height of the layer is kept greater and, while having the cooling surface unchanged, more heat can be withdrawn from the layer than with smaller throughpu-ts and correspondingly lower layers. A further advantage of the process accordingto our invention lies in the fact that the cinders obtained have a higher percentage of coarser particles and that the dust production in the :dust separators has now fallen-appreciably below the dust productionknow n to-zoccur in the prior art. practice. 3 the increasein the coarse-gra .ed component the roasted ore has become more handy for transport and further processing. a

The following examples will further illustrate this invention but the invention is not restricted to-these .ex-

amples. a

Example .1

When roastingflotationconcentrates .of pyritesaceording to theturbulent;layemoasting process, aniadditio'nal 10% .quantity'of the air used forroastingfand introduced into the turbulent layer chiefly from below throughqagrate at a uniform rate, is blown into the turbulentlayer laterally from beneath the point at which the flO'LQLlQIJ PYI'ilQS enter the furnace. The layer height of the turbulent mass, which was about cm. in its quiescent state; is thereby increased to about 50 cm. By the introduction of the additional air,,the fraction of particles in the turbulent layer having a grain size of lessthan 1 mm falls-from about smas es 7 e n A exch n t gh h exch nge ubes .Tprovidedin th v bed, and containing water and/or steam. Fresh sulfidic ore is introduced to the layer 4'adjacent the upper surface of the layer from a regulatable feeding device 10. Roasted ore or cinder is withdrawn at the opposite side of the layer through a conduit 11 adjacent -thempper surface of the grate 5, at the base of the layer.

A locally increased concentration of oxygen is provided adjacent the point of entry of the fresh ore bya oriduit 3 from the air supply leading to that;zone.- By-t ls'iaddiintroducti n of oxygen, local overheating ndconsequent partial agglomeration of ore particles L'results, increasing the average particle size in the 'fluidized'layer 4.

What We claim is:

in a process for the production of sulfur- 7 containing gases by continuously roasting finely-grained sulfidic ore having grain'sizes predominantly below about 0.2 millimeter in a fluidized layer of particles maintained uniformly in random turbulent motion thereinbynreans of the oxygen-containing gas'necessaryfor the roasting; ar d the roaster gas formed, and continuously re cinders produced by the roasting, th stepsiwhich omprise V introducing the main supply of oxygen-contain;

roasting into said layer uniformlyfrorn below viding a locally increased concentration of oxygen-con taining gas with a blast effect atanotherpoint in sa d layer by the "additional introduction :Of a subordinate 85% to 40%, whereas the fraction of particles haying a V 1 grain'size exceeding .1 mm. increasesfroml57o to 66%.

Example-2 a V continuously fed into a turbulent layer'of ,alrnostacompletely desulfurized cinders of flotation pyriteswhich layer is arranged above a grate. The hourlyinput pertsquare metre of grate surface is 850 kilograms. To maintainthe turbulent motion in the layer 1800 cubic metres of air per square metre of the grate surface are blown in per hour at a uniform rate over the whole cross-section of the grate. At the same time 180 more cubic metres of air per square metre of grate surface are blown into the turbulent a layer per hour from two separate places in the immediate vinicity of the point where the pyrites are introduced;

This supply of oxygen has the effect that localsintering ranged'immediately behind the furnace and in which Cinders with a'grain size mainlyof 0.5 to Lmillimetre The temperature of the cindcrs so re are precipitated. turned is 550 C. By these measures it is possible to increase the height of the turbulent layer to any desired extent. .As inthe roasting of coarse-grained sulfidic ores,

it is kept at a height of 50 centimetres in the quiescent state by appropriate withdrawal of agglomerated cinders from the turbulent layer. drawn from the layer per square metre of grate surface per hour 150 to .200 kilograms. Suitable cooling elements are built into the turbulent layer in order toj'mainan a temperature of 830 to 850 C.therein. I i The process described above may be visualizedon reference to the attached drawing, which is a "schematic elevational and sectional view of roasting apparatus wherein, a fluidized layer of ore is undergoing roasting according to the invention. A roasting furnace l'is pro- The amount of cinders with- T2. In..a-.process for the productioniof sulfurv dioxide-f containing gases by continuously roasting finely-grained sulfidic. ore flotationconcentrate having grain sizes ,.pre-

'dominantlybelow about 0.2 millimeter in a'fll idized; layer ofparticles maintained uniformly in random turbulent motion therein by means of the oxygenkconta' 'ng gas necessary for the roasting and the roaster gas form (1, and continuously removing the cinders produced by roasting, the steps which comprise introducin'gthe main supply of oxygen-containing gas for roasting into said layemmiformly from below, and introducing a subordinate amount of oxygen-containing gas into said layer witha-blastrefiect at another point in the layer to produce local .p artial e gglomeration of the particles in the layer. V a a 3. in a process for the production dfsulfurdioxidewcon taining' gases by continuously roasting fidic'ore having grain sizes predominantly bel 0.2 millimeterin a fluidized layer. of part1 uniformly in random turbulent motion thfir, n of the oxygen-containingvgas neceSSQIyIOrQ and the roaster gas formed, and continuouslytl a the cinders produced by the roasting, thestepsiwhich comprise introducing the main supplyof.oxygen containirig gas for roasting into said-layer uniformiy'from vbelow,and

introducing a subordinate amountflo f oxygemcontaining gas into said'layer with a blast eife ct adjaoentthe :point of introduction of the ore feed to produce loo glomeration of the particles in thelayer. V a

in a pro'cessfor the production of sulfurdioxidecontaining gases by continuously roasting finely-grained sulfidic ore having grain sizes predominantlylbclow about a 0.2 millimeter in a fluidized layer of particlesmaintained' uniformly in 'random'turbulent motion therein bylrneans of the oxygen-containing gas necessary'forthero ting and theroaster gas formed, and continuously removing yidedwhich includes a vertical refractory wall 2 defining a chamber 3. Roasting is conducted in a fluidized layer or at the base of the furnace chamber, over a 'perfor ed refractory grate '5. A wind chamber 6 is located below the grate 5, for introducing airjor iother oxygen-containing layer.

Hearts withdrawn from the layer 4by indirect heat the cinders produced by the roasting, thesteps which. corn? prise introducing the main supply of oxygen-containing .gas for roasting into 'saidlayer uniformly from below and introducing a subordinate amount of oxygenrcontaining gas together with 'ore feed into said layer with a. blast eltfect gas for roasting and fluidizin g. the

at'anothe'r point in thelay er. to produce lQQ l..-Pfii1 igglomerationof'the particles inthe layerJ j 5. l'n'a process for the production of .sulfurldio do. y grained a1 partial a g uniformly in random turbulent motion therein by means of the oxygen-containing gas necessary for the roasting and the roaster gas formed, and continuously removing the cinders produced by the roasting, the steps which comprise introducing the main supply of oxygen-containing gas for roasting into said layer uniformly from below, and introducing a subordinate amount of oxygen-containing gas together with a portion of the removed cinders into said layer with a blast effect at another point in the layer to produce local partial agglomeration of the particles in the layer, said cinders introduced with oxygencontaining gas being the coarser fraction of the flue cinders entrained by the roaster gas and having their residual heat content from the roasting.

6. In a process for the production of sulfur dioxide-containing gases by continuously roasting finely-grained sulfidic ore having grained sizes predominantly below about 0.2 millimeter in a fluidized layer of particles maintained uniformly in random turbulent motion therein by means of the oxygen-containing gas necessary for the roasting and the roaster gas formed, and continuously removing the cinders produced by the roasting, the steps which comprise introducing the main supply of oxygen-containing gas for roasting into said layer uniformly from below, and introducing a subordinate amount of oxygen-containing gas together with a portion of the removed cinders into said layer with a blast effect at another point in the layer to produce local partial agglomeration of the particles in the layer, said cinders introduced with oxygencontaining gas having their residual heat content from the roasting.

7. In a process for the production of sulfur dioxidecontaining gases by continuously roasting finely-grained sulfidic ore having grain sizes predominantly below about 0.2 millimeter in a fluidized layer of particles maintained uniformly in random turbulent motion therein by means of the oxygen-containing gas necessary for the roasting and the roaster gas formed, and continuously removing the cinders produced by the roasting, the steps which comprise introducing the main supply of oxygen-containing gas for roasting into said layer uniformly from below, and introducing a suspension of an intimate mixture of ore feed and cinders produced by the roasting in a subordinate amount of oxygen-containing gas into said layer with a blast effect at another point in the layer to produce local partial agglomeration of the particles in the layer, said cinders mixed with ore feed having their residual heat content from the roasting 8. In a process for the production of sulfur dioxidecontaining gases by continuously roasting finely-grained sulfidic ore having grained sizes predominantly below about 0.2 millimeter in a fluidized layer of particles maintained uniformly in random turbulent motion therein by means of the oxygen-containing gas necessary for the roasting and the roaster gas formed, and continuously removing the cinders produced by the roasting, the steps which comprise introducing the main supply or" oxygencontaining gas for roasting into said layer uniformly from below, and introducing a subordinate amount of oxygencontaining gas together with a portion of the removed cinders into said layer with a blast efiect at another point in the layer to produce local partial agglomeration of the particles in the layer, the amount of said cinders introduced with oxygen-containing gas being equivalent to about 20% to of the amount being produced by the roasting and said introduced cinders having their residual heat content from the roasting.

References Cited in the file of this patent UNITED STATES PATENTS 2,343,780 Lewis Mar. 7, 1944 2,563,086 Verschoor Aug. 7, 1951 2,591,595 Ogorzaly Apr. 1, 1952 2,621,118 Cyr Dec. 9, 1952 2,637,629 Lewis May 5, 1953 2,733,137 Swaine et a1 Jan. 31, 1956 

2. IN A PROCESS FOR THE PRODUCTION OF SULFUR DIOXIDE CONTAINING GASES BY CONTINUOUSLY ROASTING FINELY-GRAINED SULFURIC ORE FLOTATION CONCENTRATE HAVING GRAIN SIZES PREDOMINANTLY BELOW ABOUT 0.2 MILLIMETER IN A FLUIDIZED LAYER OF PARTICLES MAINTAINED UNIFORMLY IN RANDOM TRUBULENT MOTION THEREIN BY MEANS OF THE OXYGEN-CONTAINING GAS NECESSARY FOR THE ROASTING AND THE ROASTER GAS FORMED, AND CONTINUOUSLY REMOVING THE CINDERS PRODUCED BY THE ROAST- 